Recently, hybrid storage technology has become a trend. The hybrid storage refers to multiple different storage devices that are combined into a storage system according to a certain strategy based on different properties of different storage devices. Generally, the hybrid storage system may achieve a better system performance than a single storage system. For example, a random storage part of a central processing unit (CPU) may include a level 1 cache (L1 Cache), a level 2 cache (L2 Cache), a level 3 cache (L3 Cache), and a main storage device (main memory). Data access speeds of these storage devices gradually decrease while the capacities thereof gradually increase. According to certain cache coherence mechanisms, a large amount of data access may be performed at a cache having smaller capacity and faster speed, thereby improving an overall system performance.
The existing hybrid storage technologies mainly include a hybrid hard disk technology, a flashcache technology, etc.
The hybrid hard disk technology is directed to a hard disk in which a hybrid hard disk drive (HDD) directly integrated with a certain size solid state drive (SSD) and a technology for combining the SSD and the HDD controlled by a hard disk controller. The HDD generally has a large capacity with a slow data access speed, and the SSD generally has a small capacity with a fast data access speed. A ratio of SSD to HDD is generally fixed so that the hybrid hard disk technology is not effectively adapted to different scenarios to achieve an optimal cost performance ratio.
The flashcache technology adds a new cache layer between a virtual file system (VFS) and a device driver to implement caching popular data. The flashcache technology generally uses SSD as the media for cache (in contrast, internal memory is generally used as the cache), cache popular data from a conventional hard disk to the SSD, and uses an excellent reading performance of SSD to accelerate the system.
The hybrid hard disk technology and the flashcache technology are both hybrid mechanisms based on a single device. The single device has complex configuration and poor flexibility. Moreover, along with the development of distributed storage technology, the hybrid storage technology is also desired at a cluster level. However, the existing hybrid storage technology fails to be implemented at the cluster level.